The Stovebolt Site Forums The Shop Area Engine Shop Rochester B and Fueling Woes

1964 C60 with a brand new 292 bored .040 over with 120 miles on it. Rebuilt with stock manifolds and cam. I had purchased a rebuilt Rochester B but it had its own issues and refused to throttle back from ~2200 RPM. So I took the old Rochester that seeped, slapped it on, and the truck ran great. Barring an accelerator pump that kept off the line acceleration boggy, I could hit 55 in no time and maintain it at %80-85 throttle. Then cruising back one day I discovered that to maintain 55, I was suddenly at 95% throttle, and at 100% throttle I would get misfires. This progression continued util 95% throttle = 45mph, and then ultimately 40mph as I made it home. Front plugs were blackish grey, rears were white.

First thing I did was check all breaks, and readjust when I found a dragging rear shoe. No change. Then I pulled the old Rochester B off, whipped out the rebuild kit, qued up the videos from Mikes Carburetor Parts, and went to town. Power piston was seized, accelerator pump was shot, but everything else looked good. Thoroughly cleaned before reassembling alongside Mike's video, mimicking exactly what he spoke to. Slapped her back on the engine, warmed everything up, readjusted mixtures by ear, and low and behold a world of difference at idle. But, top speed was now 30mph. That 292 would roar and scream like a scaled cat from 1Lo thru 3Lo, start to wind out in 3Hi, and then fall flat on its face in 4. No coughing, no sputtering, just flat out foot on the floor going nowhere.

Next thought was fuel pump. Finally got it in, installed, and zero change. This time though, the carb was flooding, and this is where it gets interesting. Floats were set at standard 1 9/32 with 1 3/4 drop and the carb was slobbering fuel everywhere, turning in idle mixture all the way netted zero change, and any amount of choke on a cold engine would flood it and prevent start. I got it running with pedal on the floor, no choke, and crank. With the pto for the dump bed engaged for an engine load, I was blowing black smoke.

Off comes the carb and back to the bench again. First thing I check is my floats which are at spec. I pull out the old floats and check them. Lo-and-behold they are set at 1 13/32 with a drop of almost 2. I check the accelerator pump circuit which is working correctly, all ball valves are functioning proper, the needle and seat are sealing and there is no blow by of the needle and seat gasket. Without adjusting them, I reassembled with the old floats at the above spec and reinstalled. I am no longer flooding, I have regained mixture screw control, and no more black smoke. But, still stuck at 30 mph. Frustratingly, I advanced the distributor a tad which makes the engine run less smoothly, but I can now hit ~38 and have some guts for the 4Lo shift, but top speed is 45mph with foot on the floor and it takes 60 seconds to get there on flat road while empty.

I once again take everything apart but find nothing wrong, no indication of clogged ports, and no reasonable explanation. I slapped the spare carb back together and it still for whatever reason wont drop under 2200 rpm at idle, but that's a different topic all together.

Other things to note:
Rear axle and brakes are vacuum operated and functioning fine, thus no indication of a vacuum leak in the system (will need a gauge to verify but don't have one on hand)
From a 30 mph roll, this truck will coast a full mile and still be moving 10mph, so it isn't driveline, wheel, or brake related
The truck ran like a top until it slowly progressively just started loosing top end for no apparent reason
Brand new fuel filter with ~25 miles on it, zero particles inside of it, and no indication of any clogging
During the rebuild, I emptied the gas tank, flushed it with some seafoam, and then fresh gas, and then sealed it again and its only seen gas and Stabil since
The original Rochester Airhorn is slightly warped, but not bad enough to cause issues, just a slight weep of fuel when operating
It has to be a fueling issue because I cannot even come close to the RPM I know this engine can do in the high gears, the RPM is was cruising at just a few weeks ago

I am quite frustrated at this point and looking for any input others may have on what is going on. At this point I am not above putting these Rochesters in a cannon and firing them over the horizon and out of sight.

Let's forget about your carburetor for a minute. Something else (I believe is causing this) although you do seem to have some carburetor (and fuel pump) issues. We can certainly address those later. But for now...

Exhaust system blocked anywhere? This will cause this to happen.
Bad ignition coil. A broken down coil will cause this.
Dirty air filter. Same as exhaust blockage, really but working on the other side of the breathing affair.
Compression loss? You said the engine was rebuilt. I've seen things (unexpected things) go wrong right off the bat, so we can't rule it out.
Bad spark plugs?
Toasted vacuum advance biscuit?
Other ignition problems?

Other ignition problems can include bad plug wires, but I believe we need to focus on something that could have happened rather spontaneously. Sorry for 2 posts. Laptop has a tendency to send messages too soon.

Real carburetors fail over decades.

Rochester B's fail over several years.

The fact that your issue was almost overnight almost certainly points to an issue other than carburetion.

Like Jon G., I did read that your engine was rebuilt; however, I would still do a compression test.

Jon G.'s comment about stopped up exhaust sounds reasonable. I don't know an easy way to test this.

If the compression is good, and there is no blockage in the exhaust, then it is ignition, ignition, ignition. If you installed ANY NEW (not new old stock) ignition components, they are definitely suspect.

The poor old Rochester B deserves lots of criticism, but don't think it is the culprit this time.

Jon.

Fair points all. I honestly hadn't made the jump to ignition yet. Ill list it out to make it easier

- Brand new plug wires
- Brand new Delco plugs, PN R44XL
- Brand new complete distributor from ClassicParts, WPS DST1612 (destroyed the worn out old one to make an oil pump to prime the engine)
- New distributor had new vacuum advance biscuit

- No air filter, I am using an oil bath filter with good 50wt oil in it filled below the actual fill line to prevent any slop issues (not fall yet so its not dusty here for the moment).
- Original exhaust pipe and muffler, been waiting to get to the shop for a new setup. Muffler is shot and riddled with holes, ill just take it off altogether and run a rod down the pipes to check for any blockage. Exhaust is a simple down turn behind the cab, maybe 5 feet of 2.5in pipe in total
- Original manifolds were thoroughly inspected, cleaned, and repainted during rebuild, so there shouldn't be any blockage there

I will swing by the other shop today for the needed tool to run compression. My builder is a very renowned machinist/builder in the area and took a lot of pride in this little 6, but ill double check just to rule it out. The only part of the original engine that was kept barring external bolt-ons was the crank and head, every last other part is new.

There is no problem winding the engine out to high rpm under load (rolling empty) in the low gears, its only in high gears, thus why I have focused on fuel system up to this point. I will also note that she isn't as "jolty" in the low gears right now as she was after initially rebuilding the carb. And by jolty, I mean throttle being touchy. It was hyper responsive, more so than my 2004 Silverado.

I appreciate the feedback.

Something happened suddenly it seems. You were driving, things in high gear were ok, then something happened and now you can wind out in low gears but everything goes flat in high gears. Rusted parts inside your muffler could have fallen off while you were driving and formed a dam in there. I've seen that happen. Sudden vacuum loss is a possibility. Failed coil is a possibility, but if you're ok in lower gears it isn't a very large probability. I suppose a failed/failing gas cap is a possibility (must be vented correctly or at a point the pump can't suck enough gas)...but sort of a stretch since that would not happen suddenly.

Jon, "Rochester Bs fail over several years"? That's about the nicest and most optimistic thing I think I've heard you say about that carburetor.

Correct, but in the same post I stated REAL carburetors fail over decades

All joking aside, when I was much younger and had time to build B's for those with show vehicles who were independently wealthy (and didn't care about remaining so ) I restored several. They were generally good for about 5 years. But the time to PROPERLY do the B was about the same as to restore a dozen Rochester Q-Jets! There becomes a point where, even when one knows the time spent is there, one just doesn't feel comfortable about charging a customer.

As one ages, one learns that time is one's most valuable asset. I see no need to waste any of what I have left on a B.

Jon.

"Its never the carburetor."
I know y'all were waiting for this...
To the OP, I need to have t-shirts and hats made which state the above quote.
Personally, I always leave the carburetor for last when troubleshooting, unless fuel is pouring out of it.
In your case, it seems to me that you're having two separate problems at the same time. You found one of them. The carburetor.
Now you need to leave the carburetor alone and find the other problem. This requires a vacuum gauge, a compression tester, and a multi-meter.
Since you didn't mention that the engine dies, I don't believe that you have a fuel delivery issue.
This leaves ignition, compression and vacuum leaks.
Test all components involved in each of these areas.

I cut off the muffler last evening and am in the process of gutting it to steal the inside pipe diameter to build a quick sleeve from so I can reattach the turn-down to the pipe from the manifolds. As is it points onto the hydrovac which I dont want hot exhaust gasses hitting.Ill fire up and go for a test run today.

I replaced the gas cap during the rebuild (and filler neck). I checked it last night and it appears to vent properly (pulls air in, dopesnt let it out). Unrelated, gas makes your lips numb for a few minutes if you use your mouth...

I am with you on the distributor. The seemingly perfect operation at the low end makes me think its not, but I guess you never know.


Once I am done doing heads on the other truck today ill break out the compression gauge and check the mighty 6 and report back. As far as testing the ignition, what is the best way to do so? I am young and new to distributors as a whole, so please forgive any ignorance I may have. Ultimately want to go with HEI, but I was adamant about running with old style first to force myself to learn it in depth before ever upgrading.

Thanks for the feedback all. Ill keep digging and then report back



*EDIT*
I know you mention it above Jon, but after poking around again this morning I realized that while I replaced the distributor, I never replaced the coil pack, and lord knows how old it is. Given the seemingly fine low end, could it be breaking down at the high end with heavier loading on the engine?

Yes...it could be causing your trouble. You remember your science classes I'm certain and you recall for a coil to work you actually must have 2 coils (which inside your coil you have that). A failing coil will very often have some shorted out windings. This causes reduced inductance and while you will still have enough oomph to make a spark, it will result in lower than normal energy coming from the coil. Another thing: heat changes things inside a coil. When a failing coil gets hot (from sitting on the side of the head) it can make problems worse...meaning those shorted out windings can get a bit closer together. HEI still uses a coil but the whole HEI scheme is "high energy" oriented and will produce a more powerful spark.

Coil, See You tube for a short film on How to check a coil then turn to the condenser test. You need an ohms tester set at 20.Doc.

Oops! should have told you that the new Chinese condenser's are normally at a 50% fail rate. Keep all the old ones and hope for the best. I have a message on the web to send me all of the new old stock that can be found. I could say don't buy anything from #-@{!?5* China. I went through 3 and had problems after an hour of running. Got out one that I bought from my Dads shop in 1977, still going. Doc.

I recall having multiple failures on 216/235/261 6v condensers (from NAPA) back in the 60s/70s.

Please bear in mind if a coil is failing when hot, only testing that coil when it is hot and under operating conditions will indicate a breakdown problem or even a breakdown possibility. It may test fine when cold and it may test fine when hot but not under load. Also while there are many helpful and accurate YouTube videos, there are some which are at best misleading.

Also, some condensers claim to be still made in the USA. https://tinyurl.com/y2mhdjta And honestly I suspect some others are. Just a matter of finding them, and if they exist I can do that.

Some months ago a discussion about brake parts led into questions about whether wheel cylinders and master cylinders are still made in the USA. The answer is yes, they are. Raybestos still either makes some or has them made for them. I suspect they're made by others as I've seen master cylinders made in the USA sold also under the Cardone name and they look identical. Possible Raybestos makes and sells to Cardone, I suppose. So yes...most brake parts are made in other countries but by no means all of them.

I've contacted Standard Motor Products to ask where their condensers are made and I've added that I've read a high failure rate plagues Chinese produced condensers and have mentioned this forum (not by name...at least at this point) so they know the application of these products. Let's see what their response is. The communication was sent to their corporate office, and while it may take a while, I'm certain I'll hear from them. Using ThomasNet I've found other US makers of ignition coils and ignition products. In time I'll contact all of them and see what I find.

I wanted to give an update;

The old girl actually does not have a condenser at all. Should it? When I took ownership of the truck, besides the ignition, literally nothing electrical worked. At this point, everything but the main engine harness from the firewall to the engine/starter I have fully custom rewired as per the diagrams in my book.

While under the hood today, it hit me. At some point, in its life, someone converted the truck to 12v via whatever method they though was right, and it ran, somehow. I took close photos during the teardown and then during the reinstall, hooked it all up as per the way it was without even thinking. The ignition is hooked to the starter where the main coil supply wire is then jumped from the starter reserve straight to the positive on the coil without any ballast resistor, which has been pushing a full 12V to the points as opposed to the 9 it should be. The failure is likely in the coil (will replace with new) or in the points (hopefully not, they are brand new) because of this.

This has all flown over my head up to this point as I have followed the factory book, which having just dawned on me today, is for the old 6v system, and not the 12v one. Ill have a new resistor tomorrow and pull the cap off the points to inspect before installed the new coil and giving it a shot.

Serious gratitude to those who steered me onto the ignition route. Even if its not the problem at hand, it is a different problem that requires my attention which it has now gotten. Thank you all. I will report back with what I find.

Get a ballast resistor, get proper starter terminal adapter that energized 12v upon start, relaxes upon start to allow proper voltage through resistor to coil, then proceed.

Ed

Yes it should definitely be there. Without a condenser your engine can run for a while, but your points are going to arc so badly they're going to pit and fail quickly. The condenser is usually under the distributor cap and is a small aluminum cylinder ... about 1.25 inches long and 5/8" in diameter attached to the breaker plate however some condensers are mounted on the outside of the distributor, usually on the side. See image attached.

In another post we've been talking about condensers, how they work, alternatives to the type of condenser used in cars and things like that. If the prior owner omitted the condenser, you ought to replace the points and condenser at the same time.

I pulled off the distributor cap and sure as heck the points were running hot. I swapped the coil and rewired everything with brand new wire and connectors and hooked up the resistor. As I expected, its still not 100%, the points are fried, but I was able to make it up to 50, all-be-it not quickly nor easily. New rotator, points, and condenser coming in today. And yup I verified that the condenser is present inside the distributor.

Measuring the resistance on the coil yielded 1.5ohm. The old resistor I had measured between 1.4 - 1.5ohm and the new one I have which is rated at 1.8ohm is measuring at 2.2ohm. Referencing old threads here on the forums shows that 3ohm collectively is the desired goal. Will running higher that 3 have any ill effects? Just curious.

Unrelated note:
I know many people absolutely love the throb of a straight 6 and I never really understood it, until i dropped the muffler and ran without it. That fresh 292 makes a very healthy sound unlike any V8 I know.

And once again, thank you to everyone that has chimed in on this thread, I greatly appreciate all your input.

My big 6(503) has a nice sound, too, different than smaller 6’s because of the different firing order, unlike a V-8 sound.

Ed

Unless you're trying to build some sort of 100% original show truck, the fix for a 292 is to install the HEI ignition distributor that's on the later model 250's and 292's. Your electrical system is already 12 volts, so the only other modification needed will be a #12 or larger power wire from the ignition switch to the distributor. HEI's were invented to meet the government requirement that any system that has an effect on exhaust emissions must be able to run 50K miles without being serviced.
Jerry

That is the end state plan here, but I actually wanted to start on points. I want to spend the first year or so on points to learn it inside and out, and then when I switch to HEI the points will go right to the glovebox so if I ever have a problem on the road, I can swap the points back in and get home since points can be jerry rigged and repaired on the roadside, HEI cannot always be done so.

I understand most don't like points, but its where it all started, and I want to know that system inside and out, even if it is just to truly appreciate where we now are without it. Call me sentimental I suppose; born a couple generations too late.

Just so we're clear...these are 2 completely different designs. You can switch back to points only if you swap the entire distributor, the coil, the resistor, the spark plugs (remember please the HEI plugs will be gapped wider), the condenser, the rotor, the points and the distributor cap. In other words...everything that went with the points system. Unless you use one of the Pertronix modules (which is very likely to leave you stranded and highly agitated somewhere far away at some unpredictable time). If on the other hand you go with the GM made HEI (as Jerry has advised) you'll have a system which is simpler and has shown a high likelihood of not failing. Good luck!

Having read through this thread, I agree it's the ignition. Have you had the chance to fix it?

There's a nice clear space on one wall of my shop, with nothing whatsoever on it. I think I'll go out there and talk to it for a while. At least it doesn't argue, ignore me, misinterpret what I'm saying, or deliberately do something 180 degrees opposite of what I suggest!
Jerry

If it helps, Jerry, I will be adding HEI with proper plugs, wires and plug gaps to my 292 before initial fire-up.